1. Field of the Invention
The present invention relates to a toothbrush comprising both soft and hard bristles, a toothbrush that can act as both soft and firm toothbrush.
2. Description of Prior Art
The toothbrushes on the market nowadays are classified into three categories: Soft, medium and firm according to the degree of hardness of the bristles.
Firm toothbrushes, having hard bristles, clean plaque better. They have two drawbacks:
a. The hard bristles may hurt gums. PA1 b. Outward bent hard bristles of an old toothbrush may hurt the membrane inside the mouth while brushing the teeth.
However, the problem with soft toothbrushes is that they are unable to clean the space between the teeth effectively. Bristles of soft toothbrushes are either unable to be inserted into the narrow space between the teeth, or are unable to remove plaque after they are inserted there. Efforts were made in U.S. Pat. Nos. 3,934,298, 4,633,542, 4,72,4569, 5,184,368, and 4,694,844 to get better access between the teeth. None of them have bristles hard enough for cleaning, especially the space between the teeth.
Medium toothbrushes cannot meet all these needs because some teeth need harder cleaning, others need minor cleaning, while gums need just a massaging.